Granular surface avalanching induced by drainage from a narrow silo
Granular surface avalanching induced by drainage from a narrow silo
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狭窄筒仓排水引起的颗粒表面雪崩
DOI：
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发表时间：
2018
影响因子：
3.7
通讯作者：
H. Capart
中科院分区：
文献类型：
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作者：
C. Hung;P. Aussillous;H. Capart
利用理论和实验，我们研究了由于物料从狭窄筒仓流出而导致的颗粒表面雪崩。假设的筒仓几何形状是一个深矩形盒子，具有适中的跨度宽度和平滑的前壁和后壁之间的小间隙厚度。自由表面下方深处的一个小孔让颗粒以恒定的速度排出。因此，在大部分表面下降历史中，所得到的颗粒流可以被假定为准二维且准稳定的。为了模拟这些流动，我们将深层颗粒流的运动学模型与浅层表面雪崩的动态模型结合起来。然后，我们将计算出的流场与详细的粒子跟踪测量结果进行比较，让筒仓相对于高速摄像机上升以提高空间分辨率。结果表明，雪崩表面形状和近地表流动是由沉降速度的展向梯度控制的，而该梯度又是如何由孔口上方的高度和间隙厚度控制的。深层流动模式与速率无关，而浅层雪崩则由颗粒流变学控制。
Using theory and experiments, we investigate granular surface avalanching due to material outflow from a narrow silo. The assumed silo geometry is a deep rectangular box, of moderate spanwise width and small gap thickness between smooth front and back walls. A small orifice deep below the free surface lets grains drain out at a constant rate. The resulting granular flows can therefore be assumed quasi-two-dimensional and quasi-steady over most of the surface descent history. To model these flows, we couple a kinematic model of deep granular flow with a dynamic model of shallow surface avalanching. We then compare the calculated flow fields with detailed particle tracking measurements, letting the silo ascend relative to the high-speed camera to increase spatial resolution. The results show that the avalanching surface shape and near-surface flow are controlled by the spanwise gradient in subsidence velocity, and how this gradient is in turn controlled by the height above orifice and the gap thickness. Whereas the deep flow pattern is rate independent, shallow avalanching is paced by the granular rheology.